improve help

@@ -322,7 +322,7 @@ int main(int argc, char * argv[])
 		printf("   merge_av 1.0.0\n");
 		printf("   run ffmpeg to merge audio and video files according to the record info file,\nusage:");
 		printf("\n   %s record_info_filename [-p] [-k]", argv[0]);
-		printf("\n   -p :only print the command,don't run ffmpeg\n");
+		printf("\n   -p :only print the command,don't run ffmpeg");
 		printf("\n   -k :keep the temp files\n");
 		return -1;
 	}